Self-contained foam fire extinguishing system

ABSTRACT

A self-contained high expansion foam fire extinguishing system providing an independent source of pressurization to a container holding a mixture of water and foam concentrate for delivery to a foam generator having a plurality of nozzle members and a stratified screen to produce high expansion foam upon activation of the system by a fire detecting sensor.

United States Patent 1 Stults [451 Jan. 9, 1973 [54] SELILCONTAINED FOAMFIRE g Regan et a1. 016192195);

, 1 arnes EXTINGUISHING SYSTEM 3,465,827 9/1969 Levy et al v.169/15 X[76] Inventor: Howard C. Stults, 7630 South 2,826,399 3/1958 Eriksson..l69/15 X Bright, Whittier, i 90 02 1 3,241,617 3/1966 Jamison ..l69/153,356,148 12/1967 Jamison ..169/15 [22] Filed: July 8, 1971 PrimaryExaminer-Allen N. Knowles [21] Appl' 160810 Assistant Exam'inerMichae1M'ar Relaed Appncafion Data Attorney-Spensley, Horn & Lubitz [63]Continuation-impart of Ser. No. 782,343, Dec. 9, [57] ABSTRACT 1960, Pt. N 3,592,269.

a o A self-contained high expansion foam fire extinguish- [52] U S Cl169/9 239/590 3 ing system providing an independent source of pres- 51 It Cl 3 'surization to a container holding a mixture of water 1 I: u cand foam concentrate for delivery to a foam generator [58] held ofSearch "169/2, 15; 239/343 having a plurality of nozzle members and astratified 590-5 screen to produce high expansion foam upon activa--tion of the system by a tire detecting sensor. [56] References Cited 15Claims, 8 Drawing Figures UNITED STATES PATENTS 3,342,271 9/1967Anthony, Jr ..169/9 X SELF-CONTAINED FOAM FIRE EXTINGUISl-IING SYSTEMThis is a continuation-in-part of my co-pending application Ser. No.782,343 filed Dec. 9, 1968 now U.S. Pat. No. 3,592,269.

BACKGROUND OF THE INVENTION 1. Field of the Invention This inventionrelates to a new type of foam fire extinguishing system of the typehaving a storage tank for foam producing matter. A foam generator forproducing foam, said system especially adapted for installation in astore or other structures.

2. Prior Art A self-contained efficient and highly reliable highexpansion foam system for the extinguishing of a fire in a building haslong been a desired goal. High expansion foam is a relatively newdevelopment for fighting fires, especially in buildings or otherenclosed structures. The prior art discloses some high expansion foamfire fighting devices, both portable and fixed installations. For thepurposes of this invention, the term high expansion foam will beunderstood to define a foam which expands a given volume of watertogether with a concentrated mix (in solution) from 300 to 1,500 timesits original volume.

One of the devices disclosed by the prior art generates high expansionfoam through the use of a source of foam concentrate, but requires thatair be mixed therewith through an air stream created by rotation of anexternal fan. The foam is formed by the flowing of air through a screenafter the stream has been wet with the spray of foam concentrate. Thisdevice specifically requires the use of a fan to inject the air requiredto form the foam.

The present invention solves the need for external air moving equipmentand uses no force other than the partial vacuum created by the flow offoam concentrate to draw in ambient air. The ambient air is drawn in bythe partial vacuum without the need of any fan or other air movingequipment.

Another device disclosed by the prior art requires a tubular casingenclosing two sets of nozzles, the first set being connected to a sourceof foam concentrate, the second set of nozzles being connected to asource of carbon dioxide. A foam forming net is disposed in front of thetwo sets of nozzles to produce foam from the mixture of carbon dioxideand foam concentrate. The device requires the combined action of carbondioxide and the foam producing concentrate and as a result requires theinclusion of additional pressurizing equipment and nozzles for thedisposition of carbon dioxide. The present invention requires noadditional source of mixing agent and therefore obviates the problemsraised by the described device. In the present invention, the air isdrawn into the foam generator solely as a result of the partial vacuumcreated by the output of foam concentrate.

SUMMARY OF THE INVENTION The basic problem to be solved by the presentinvention system is to provide a high expansion foam generating systemto be used as a fire fighting system, and which is completelyself-contained and therefore substantially independent of externalconditions.

The high expansion foam fire extinguishing system utilizes a pre-mixedhigh expansion foam concentrate. When a sensor detects the presence of afire, a valve is opened, placing the high expansion foam concentrateunder pressure from an inert gas, typically gaseous nitrogen. Placingthe high expansion foam concentrate under pressure forces theconcentrated mixture into a manifold having a plurality of attachednozzles. When the concentrated mixture is forced through the nozzle, acone of liquid concentrate is emitted.

The cone of liquid concentrate is emitted into a foam generator definedby an upper wall, a bottom wall, a pair of side walls, a rear wall and ascreen. The structure of the foam generator insures that the stratifiedscreen is substantially parallel with the floor or other surface of theenclosure within which the present invention is disposed. The top wallsand bottom wall of the foam generator extend upwardly from the screenand at an angle therefrom. The bottom wall is terminated a suitabledistance from the screen to permit insertion of the foam concentrateinput and the foam emitting nozzles. The top wall is terminated by arear wall of the foam generator, the foam generator being enclosed byappropriate side walls. As mentioned, the foam concentrate input isinserted through an opening of the foam generator formed by the bottomwall, rear wall and side walls of the foam generator. The manifold offoam emitting nozzles is disposed within the interior of the foamgenerator, the nozzles being directed toward the screen. The axis of thecone of foam concentrate is substantially parallel to the angle of thetop and bottom walls of the foam generator.

The foam is formed by a combination of air and high expansion foamconcentrate striking the screen. Air is drawn through the orificedefined by the bottom, rear and side walls of the foam generator. Asubstantial portion of the air heated by the fire will only enter thefoam generator at this formed orifice because the upper wall and rearwall fully covers the nozzle output.

The screen constitutes a multi-layer structure, the first layer being ametallic honeycombed sheet, the bottom layer of the screen being ametallic mesh structure The honeycombed screen and mesh structureprovide a suitable ratio of hole area to surface area to utilize theavailable free energy in the vicinity of the screen openings. Thenozzles are spaced along the manifold at a predetermined distance thatis necessary to insure full coverage of the screen surface. Since thecones formed by emitted concentrate fully cover the screen, the systemconstitutes a linear generator in that an even distribution of foam iscreated along the entire length of the foam generator. The nozzles aredisposed at an angle with respect to the floor of the enclosure toprovide that the axis of the cone of emitted foam concentrate issubstantially parallel to the top and bottom walls of foam generator andalso to provide substantially uniform distribution across the screen.

The foam emitted from the screen is directed downward because of theorientation of the screen. The heated air is drawn through the foamcooling the air. The foam will continue to be generated cooling theentire area of the building. Since the foam has a high water content,the fire will be extinguished. The high expansion foam concentratecontains a detergent which acts to clean the inner areas of thebuildings as well as extinguish the fire.

It is therefore an object of the invention to provide a fireextinguishing system which is independent of external water supplies,pressurization and electric power.

It is a further object of the invention to provide a selfcontained fireextinguishing system which utilizes a high expansion foam concentrate.

It is still a further object of the invention to provide a foamgenerator without the use of motors, fans or other air moving devices.

A still further object of the invention is to provide a linear foamgenerator.

The novel features which are believed to be characteristic of theinvention, both as to its organization and method of operation, togetherwith further objectives and advantages thereof will be better understoodfrom the following description considered in connection with theaccompanying drawing in which a presently preferred embodiment of theinvention is illustrated by way of example. It is to be expresslyunderstood, however, that the drawing is for the purpose of illustrationand description only, and is not intended as a definition of the limitsof the invention.

BRIEF DESCRIPTION OF THE DRAWING FIG. la is a partial sectional viewshowing the presently preferred embodiment of this invention installedwithin a building and the manner in which it is employed to extinguish afire which may have occurred within the building.

FIG. lb is an alternative embodiment of the pressure system for thefluid and compressed gas motive means shown in FIG. 1.

FIG. 2 is an enlarged cross-sectional view showing the foam generatorportion of FIG. 1 enlarged in size.

FIG. 3 is an enlarged perspective view of the foam generator of FIG. 1.

FIG. 4 is a plan fragmentary view of the multilayer screen forming partof the generator of FIG. 3.

FIG. 5 is a partial cross sectional view of the multilayer screen takenalong lines 55 of FIG. 4.

FIG. 6 is an enlarged sectional view of an exemplary nozzle as may bestbe seen in FIG. 3 forming part of the generator.

FIG. 7 is a schematic view showing the discharge cone of the fluidsolution as it exists from one of the nozzles forming part of thegenerator of the present invention system.

DESCRIPTION OF THE PREFERRED EMBODIMENTS Reference is now made to FIG.la, wherein a presently preferred embodiment of this invention is showninstalled within an appropriate enclosure generally designated by thereference numeral 10. The foam generator is generally designated by thenumeral 20 as shown extended from the ceiling or roof ll of enclosure I0by cables or chain 12. The exterior wall of the storage building 10 isnumbered 13 and the interior wall 14. The ground or the floor of thebuilding is numbered 15. The present invention foam system isselfcontained and requires no external source of electric power,hydraulic power or gas power. Included within the system, in order togenerate foam upon the occurrence of a fire within a building l0,thereis provided a source of inert gas such as nitrogen under pressure shownwithin a container 21. Container 21 is connected through an appropriateline 22 to a valve-pressure regulator 23 to a concentrate mix solutiontank 24. A line 39 exits from tank 24 and connects to a manifold 25through an opening 26 in the wall 14. Foam generator 20 is constructedof top wall 27, bottom wall 28, rear wall 29 and a pair of side wallsenclosing a cavity between top wall 27, bottom wall 28 and rear wall 29.As shown in FIG. la and FIG. 2, top wall 27 is typically suspended fromceiling 11 by chain 12, top wall 27 and bottom wall 28 beingsubstantially parallel. In addition, an additional bottom portion 30depends from rear wall 29 co-planar with bottom wall 28, bottom walls 28and 30 defining an orifice therebetween. Side walls not shown in FIG. 1aand FIG. 2 are coupled to the side surfaces of top wall 27, rear wall 29and bottom walls 28 and 3.0 to fully define the orifice opening into theinner cavity of foam generator 20.

The portions of top wall 27 and bottom wall 28 nearest floor 15 areadapted to receive multilayer screen 31. Multilayer screen 31 issubstantially parallel to floor 15. As can be seen in FIG. 2, multilayerscreen 31 is comprised of a honeycombed layer 32 and an outer mesh layer33. The details relating to honeycombed layer 32 and mesh layer 33 shallbe explained in detail below.

Referring again to FIG. 1a, the foam system is activated when sensor 34detects the presence of heat incident to a fire. Sensor 34 is a heatdetector which initiates an alarm upon detecting an ambient temperaturetypically at a value of 135F. Sensor 34 is a conventional heat detectorof the type manufactured by the Walter Kidde Corporation. The output ofsensor 34 appears on line- 35 and energizesa relay pack 36 whichproduces an electrical signal on signal lines 37 to the valve pressureregulator 23. Valve-pressure regulator 23 is an electrically activateddevice regulating the pressure to be imposed upon the concentrate mixsolution tank 24. The valve-pressure regulator 23 can be set for outletpressures typically in the range of 20-40 psi. One of the advantages ofthe present invention selfcontained fire extinguishing system is topermit the generation of large quantities of foam while requiring onlylow pressure equipment for movement of the foam concentrate. Where thestructure of the present invention utilizes a set of eleven foamemitting nozzles to be designated as APCO No. 80350lD-3. By openingvalve-pressure regulator 23, the gaseous contents of container 21 iscaused to flow through line 22, pressure regulator 23, line 38 and intothe concentrate mix solution tank 24. Since the concentrate mix incontainer tank 24 is under pressure, the mixture is forced into line 39.

The high expansion foam concentrate is typically by weight composed to3.0 to 4.5 percent Neodol 25, 30

'to 35 percent Neodol 23-3A, 26 to 30 percent butyl ether dietheoleneglycol and the balance of 30.5 to 41 percent of water. The concentrateis further diluted by volume to a concentration of 3 percent of theabove foam concentrate and 97.0 percent water. Neodol 23-3A is definedin "Shell Chemical Bulletin, I.C.:674l and is an aqueous solution ofammonium salt of a sulfated primary alcohol ethyoxylate containing onthe average three ethylene oxide units. Neodol 233A can be characterizedby a molecular weight of approximately 423, a concentrate of ethyleneoxide by weight of 31.2 percent, a specific gravity at 25C of 1.01, anda pH of 7.3. It is a light colored viscous liquid containing about 60percent by weight surfactant and ethanol is included as a solubilizor.Neodol 25 is commercially available from the Shell Chemical Company.Neodol 25 designates an alcohol blend characterized by the symbol ROHwhere R is a blend of linear primary alcohols with 12, 13, 14 and 15carbon atoms. The physical characteristics of Neodol 25 are a molecularweight of approximately 207, a specific gravity at 25C of 0.834, and aviscosity of 18.3 centipoise at 100F. A high expansion foam isdistinguishable from low expansion foam concentrate by the expansionratio which is defined by the volume of foam produced divided by theoriginal volume of the concentrate. A high expansion concentrate has anexpansion ratio of 300 to 1,500 while a low expansion concentrate has anexpansion ratio of 10 to 20. The preferable ratio for use in buildingsis 600 to 700. The expansion ratio can be changed by changing thepressure imposed on the concentrate. Referring to FIG. 1a, thevalvepressure regulator 23 can be set for a pressure of 25 40 psi. Whenthe pressure is applied to the concentrate mix solution tank 24, theconcentrate will have an expansion ratio substantially in the range of500 700. The amount of concentrate available for fire fighting can beincreased by putting a plurality of solution tanks 24 in series.Referring to FIG. 1b, in which an alternate form for the source of foamconcentrate is shown, three solution tanks 24 are serially connectedwith the result approximately three times more foam can be produced. Byputting a plurality of pressure sources and solution tanks 24 inparallel, the volume per unit of time of foam generated can beincreased.

An understanding of the generation of foam can be best gained byreference to FIG. 2. The concentrate is forced into line 39 and intomanifold 25 with a resulting emission of concentrate at nozzle 60. Thenozzle 60 can be attached to manifold 25 in any suitable manner butpreferably by a threaded joint 62 as shown in FIG. 6. The nozzle 60 canhave a spiral chamber 64 leading to an annular flanged output 66 whichwill produce an output emission forming a cone. The nozzle 60 separationalong manifold 25 can be best seen in FIG. 3. The number of nozzles 60coupled to manifold 25 can be any suitable number which will insureuniform distribution of solution upon multilayer screen 31, thepreferred embodiment of the present invention utilizing a set of 11nozzles 60 within each foam generator 20. The concentrate cone 68emitted by a nozzle 60 is such that all parts of the multilayer screen31 will be reached by the concentrate. If 1 l nozzles 60 are spacedalong manifold 25 of a generator 20, nitrogen pressure of 35 psi willproduce 1,500 cubic feet of foam per minute. If the nozzle 60 separationis reduced or the nitrogen pressure increased, the foam generated perfoot of generator will be substantially increased. The surface areacreated by the concentrate cone 68 (FIG. 7) is intersected by the foamgenerating screen 31. As shown in FIG. 2, multilayer screen 31 isattached to top wall 27 and bottom wall 28 in a manner which will insurethat multilayer screen 31 is substantially parallel to floor 15.Although the angle of top wall 27 with respect to floor 15 can be anysuitable angle, it is preferably disposed at'approximately 45 i 15 withrespect to the surface of floor 15. Nozzles are oriented with respect tothe plane of top wall 27 and bottom wall 28 to insure that the cone offoam concentrate 68 is uniformly distributed across multilayer screen31. This is accomplished by making the axis of the cone 68 substantiallyparallel to top wall 27 and bottom wall 28.

Although the preferred embodiment of the present invention is adapted tobe used within fixed structures and secured as shown in FIG. 10, it iswithin the scope of the present invention to provide for other means ofsupporting foam generator 20 and to use the system within any enclosedstructure such as marine vessels and aircraft.

Referring now to FIG. 4 and FIG. 5, the structure of multilayer screen31 can be best understood. In order to adapt multilayer screen 31 toproduce the highest flow rate of foam, the surface area between theholes must be expanded to increase agitation. As set forth inApplicant's co-pending application, Ser. No. 782,343 filed Dec. 9, 1968,hammertone or crackle paint which increases the surface area is asolution to this problem. The present invention is. substantiallyimproved by utilizing multilayer screen 31. Honeycombed layer 32substantially increases the surface area available for contact by thefoam concentrate thereby providing a greater surface area for increasingagitation. In addition, honeycombed layer 32 substantially increases thehole area to allow a greater flow of generated foam. Honeycombed layer32 constitutes a plurality of adjacent hexagonal orifices 70 bounded bythe metallic honeycombed walls 71 forming honeycombed layer 32.Honeycombed layer 32 is selected to provide a proper balance between thesurface area provided by metallic walls 71 and hexagonal orifices 70.Although it is within the scope of the invention to utilize anyappropriate honeycombed layer 32, the preferred embodiment of thepresent invention utilizes honeycombed structure fabricated of raw oroxidized aluminum wherein the distance between opposed wall junctions oforifices 70 is approximately one-fourth inch. To provide adequatesurface area, honeycombed layer 32 is approximately one-half inch thick.

The outer layer of multilayer screen 31 is mesh layer 33. Mesh layer 33is a metallic wire mesh preferably having a mesh substantially in theform of a diamond honeycomb. Mesh layer 33 is an appropriate metalpreferably adapted to be plated with metals having high oxidationpotentials. A metal is typically described as an active'metal where ithas a high oxidation potential, i.e., higher than 0.4, as shown in theTable of Potentials of Electrochemical Reactions in the Handbook ofChemistry and Physics, D86 (49th ed., '1 968). A typical set of activemetals'meeting the above requirements are cadmium, zinc, chromium andplatinum. Mesh layer 33 is preferably fabricated of carbon steel platedwith cadmium or zinc. The combination of honeycomb layer 32 and meshlayer 33 substantially increases the agitation of the foam concentrateproducing a greater flow rate at lower pressure. in addition, the foamproduced is substantially more homogenious permitting greaterpenetration of the area to be filled by the foam.

The operation of the present invention fire extinguishing system can bebest seen by reference to FIG. 1a and FIG. 2 wherein foam generators areshown emitting foam within the enclosed structure. As can be seen inFIG. 2, foam generator 20 is constructed to insure that the multilayerscreen 31 is substantially horizontal and therefore parallel to thefloor of structure 10. Top wall 27 and bottom walls 28 and 30 aresubstantially parallel, top wall 27 and bottom wall 30 being joined byrear wall 29. Top wall 27 is joined to bottom wall 28 at the lower edgesthereof by multilayer screen 31. The lateral edges of walls 28 30 arejoined by side walls not shown. The fabricated walls of foam generatorprovide for an orifice between bottom walls 28 and 30 through which aircan be drawn for mixing with the cone 68 of foam concentrate to producethe generated foam.

Pressurized foam concentrate held in container 24 is forced throughmanifold 25 and from nozzles 60 producing cone 68 of foam concentrate tocontact multilayer screen 31. As stated, the fiow axis of cone 68 offoam concentrate is substantially parallel to top wall 27 and bottomwall 28 to provide for substantially uniform distribution of the foamconcentrate on honeycombed layer 32 of multilayer screen 31. The conicstream 68 of foam concentrate creates a partial vacuum drawing theheated air 74 into orifice 73 defined by bottom wall 28, bottom wall 30and the side walls joining walls 28 30. The mixture of air and the foamconcentrate produces foam pile 75 through which heated air 74 is drawn.As stated, orifice 73 through which the partial vacuum draws heated air74 is defined by an opening in bottom walls 28 and 30 laterally boundedby the side walls of foam generator 20. The drawing of heated air 74through foam pile 75 substantially cools heated air 74 therebyaccelerating the fire extinguishing process. Drawing heated air 74through foam pile 75 is assured since top wall 27 and rear wall 29substantially shroud nozzles 60 thereby leaving the only point of entryat orifice 73. Heated air 74 will carry particles emanating from burningarticle 76 and this in turn, will particularly contaminate cone 68 offoam concentrate as can be seen in FIG. 7. The outer surface or skin ofthe cone 68 of concentrate will be impregnated with the contaminatingparticles but so long as the velocity of the concentrate is sufficientto prevent total impregnation of the cone 68, foam generation atmultilayer screen 31 will be effective.

The present invention fire extinguishing system produces a device whichsubstantially solves problems existing in those devices disclosed by theprior art. The present invention system is totally self-containedrequiring no external means for drawing air or other catalysts into foamgenerator 20 to combine with the foam concentrate for the generation offoam. Air is drawn through orifice 73 without the need of any fans orother air moving equipment. The combined mixture of foam concentrate andair strikes multilayer screen 31 thereby producing sufficient agitationto produce a stream of foam. Multilayer screen 31 comprising honeycombedlayer 32 and mesh layer 33 produces substantially equivalent flow ratesof foam at substan tially lower pressures. The effect of these resultspermits the fabrication of a self-contained fire extinguishing system atsubstantially lower costs and without the problems inherent, in thosedevices described by the prior art lclaim:

1. An improved fire extinguishing system of the type employing highexpansion foam, the improvement comprising: 7

a. a reservoir containing a pre-mixed, high expansion foam producingfluid;

b. a foam generator comprising:

1. a plurality of nozzle members coupled to said reservoir; v

a multilayer screen horizontally disposed and opposite said nozzles,said foam generator having top, bottom, rear and side enclosures, saidbottom enclosure extending from said multilayer screen to a distancesubstantially in the vicinity of said nozzles and said top enclosureextending from said multilayer screen substantially beyond said nozzles,said rear enclosure depending downwardly from said top enclosuredefining an orifice whereby air is drawn into said foam generatorthrough said orifice defined by said enclosures when fluid is caused tobe discharged through said nozzles for projection upon said'multilayerscreen where said high expansion foam is generated.

2. The fire extinguishing system as defined in claim 1 wherein saidmultilayer screen comprises a first honeycombed layer having a pluralityof hexagonal cells disposed therethrough and a second mesh layer inintimate contact with said first honeycombed layer.

3. A fire extinguishing system as defined in claim 2 wherein said secondmesh layer is plated with an active metal selected from a groupconsisting of cadmium, zinc, chromium and platinum.

4. A fire extinguishing system as defined in claim 1 including apressurized source of inert gas, said pressurized source being coupledto said reservoir whereby said foam producing fluid is forced out ofsaid nozzles.

5. A fire extinguishing system as defined in claim 4 wherein saidpressurized source is pressurized in the range of 25 to 40 psi.

6. A fire extinguishing system as defined in claim 4 wherein said inertgas is nitrogen.

7. A fire extinguishing system of the type using high expansion foamcomprising:

a. self-contained source means for containing pressurized gas;

b. reservoir means coupled to said self-contained source means forcontaining a pre-mixed high expansion foam producing concentrate;

c. foam generating means for drawing airinto same and generating foamcoupled to said reservoir means, said foam generating means comprising:

1. a manifold having spaced openings therein coupled to said reservoirmeans;

2. a plurality of nozzles coupled to said spaced openings in saidmanifold, said nozzlesadapted to output said foam producing concentrate;

3. a multilayer screen horizontally disposed and being opposite saidnozzles, said multilayer screen comprising a first honeycombed layerhaving a plurality of hexagonal cells disposed therethrough and a secondmesh layer in intimate contact with said first honeycombed layer; and

4. an enclosure having top, bottom, rear and side walls, a portion ofsaid top wall and said bottom wall being coupled to said multilayerscreen, said enclosure defining an orifice through said bottom wallwhereby the output of foam producing concentrate from said nozzlescauses ambient air to be drawn through said orifice.

8. A fire extinguishing system as defined in claim 7 wherein said secondmesh layer is plated with an active metal selected from a groupconsisting of cadmium, zinc, chromium and platinum.

9. A fire extinguishing system as defined in claim 7 wherein saidpressurized gas is an inert gas.

10. A fire extinguishing system as defined in claim 9 wherein said inertgas is nitrogen.

11. A fire extinguishing system as defined in claim 7 wherein saidself-contained source means is pressurized in the range of 25 40 psi.

12. A self-contained fire extinguishing system of the type using highexpansion foam comprising:

a. a source of pressurized, inert gas;

b. at least one reservoir adapted to contain high expansion foamproducing fluid, said reservoir coupled to said source of pressurized,inert gas; and

c. a foam generator having an enclosure of top, bottom, rear and sidewalls defining an orifice through said bottom wall, a multilayer screenincluding a first honey-combed layer and a second plated mesh layer,said multilayer screen being horizontally disposed and secured toportions of said top and bottom walls, a manifold having a plurality ofspaced openings therein being disposed within said enclosure and coupledto said reservoir, and a plu rality of nozzles each being coupled to oneof said spaced openings and being opposite said multilaycr screen andadapted to output said foam producing fluid uniformly upon saidmultilayer screen whereby the output of said foam producing fluid fromsaid plurality of nozzles causes ambient air to be drawn through saidorifice.

13. A fire extinguishing system as defined in claim 12 wherein said meshlayer is plated with an active metal selected from a group consisting ofcadmium, zinc, chromium and platinum.

14. A fire extinguishing system as defined in claim 12 wherein saidinert gas is nitrogen.

15. A fire extinguishing system as defined in claim 12 wherein saidinert gas is pressurized in the range of 25 40 psi.

2. a multilayer screen horizontally disposed and opposite said nozzles,said foam generator having top, bottom, rear and side enclosures, saidbottom enclosure extending from said multilayer screen to a distancesubstantially in the vicinity of said nozzles and said top enclosureextending from said multilayer screen substantially beyond said nozzles,said rear enclosure depending downwardly from said top enclosuredefining an orifice whereby air is drawn into said foam generatorthrough said orifice defined by said enclosures when fluid is caused tobe discharged through said nozzles for projection upon said multilayerscreen where said high expansion foam is generated.
 2. a plurality ofnozzles coupled to Said spaced openings in said manifold, said nozzlesadapted to output said foam producing concentrate;
 2. The fireextinguishing system as defined in claim 1 wherein said multilayerscreen comprises a first honeycombed layer having a plurality ofhexagonal cells disposed therethrough and a second mesh layer inintimate contact with said first honeycombed layer.
 3. a multilayerscreen horizontally disposed and being opposite said nozzles, saidmultilayer screen comprising a first honeycombed layer having aplurality of hexagonal cells disposed therethrough and a second meshlayer in intimate contact with said first honeycombed layer; and
 3. Afire extinguishing system as defined in claim 2 wherein said second meshlayer is plated with an active metal selected from a group consisting ofcadmium, zinc, chromium and platinum.
 4. an enclosure having top,bottom, rear and side walls, a portion of said top wall and said bottomwall being coupled to said multilayer screen, said enclosure defining anorifice through said bottom wall whereby the output of foam producingconcentrate from said nozzles causes ambient air to be drawn throughsaid orifice.
 4. A fire extinguishing system as defined in claim 1including a pressurized source of inert gas, said pressurized sourcebeing coupled to said reservoir whereby said foam producing fluid isforced out of said nozzles.
 5. A fire extinguishing system as defined inclaim 4 wherein said pressurized source is pressurized in the range of25 to 40 psi.
 6. A fire extinguishing system as defined in claim 4wherein said inert gas is nitrogen.
 7. A fire extinguishing system ofthe type using high expansion foam comprising: a. self-contained sourcemeans for containing pressurized gas; b. reservoir means coupled to saidself-contained source means for containing a pre-mixed high expansionfoam producing concentrate; c. foam generating means for drawing airinto same and generating foam coupled to said reservoir means, said foamgenerating means comprising:
 8. A fire extinguishing system as definedin claim 7 wherein said second mesh layer is plated with an active metalselected from a group consisting of cadmium, zinc, chromium andplatinum.
 9. A fire extinguishing system as defined in claim 7 whereinsaid pressurized gas is an inert gas.
 10. A fire extinguishing system asdefined in claim 9 wherein said inert gas is nitrogen.
 11. A fireextinguishing system as defined in claim 7 wherein said self-containedsource means is pressurized in the range of 25 - 40 psi.
 12. Aself-contained fire extinguishing system of the type using highexpansion foam comprising: a. a source of pressurized, inert gas; b. atleast one reservoir adapted to contain high expansion foam producingfluid, said reservoir coupled to said source of pressurized, inert gas;and c. a foam generator having an enclosure of top, bottom, rear andside walls defining an orifice through said bottom wall, a multilayerscreen including a first honey-combed layer and a second plated meshlayer, said multilayer screen being horizontally disposed and secured toportions of said top and bottom walls, a manifold having a plurality ofspaced openings therein being disposed within said enclosure and coupledto said reservoir, and a plurality of nozzles each being coupled to oneof said spaced openings and being opposite said multilayer screen andadapted to output said foam producing fluid uniformly upon saidmultilayer screen whereby the output of said foam producing fluid fromsaid plurality of nozzles causes ambient air to be drawn through saidorifice.
 13. A fire extinguishing system as defined in claim 12 whereinsaid mesh layer is plated with an active metal selected from a groupconsisting of cadmium, zinc, chromium and platinum.
 14. A fireextinguishing system as defined in claim 12 wherein said inert gas isnitrogen.
 15. A fire extinguishing system as defined in claim 12 whereinsaid inert gas is pressurized in the range of 25 - 40 psi.